| 摘要 |
PURPOSE:To prevent the damage, erroneous indication and malfunction of a meter by providing upper-limit and lower-limit gate circuits that permit a received pulse to pass through them in accordance with the upper-limit and lower-limit levels of a reservoir level and then by performing switching by outputs of those gate circuits. CONSTITUTION:A reference pulse from reference-pulse generating circuit 1 is sent as an ultrasonic wave pulse to a tank bottom part by way of transmitter 6 and its reflected wave is detected through receiver 7, so that so far as the received pulse is normally obtained, a meter displays the normal level of the contents of the tank. The reference pulse, on the other hand, is input to the 1st and 2nd monostable multivibrators 13 and 14, which outputs upper-limit and lower-limit gate pulses respectively. Since R-S flip-flop 2 is supplied with the trailing edge of the lower- limit gate pulse in every period of the reference pulse, flip-flop 2 is reset at fixed timing without fail even when the reflected wave is interrupted, so that an excessive input to the meter can be prevented. |
